1. Field of the Invention
This invention relates to drilling heads and blowout preventors for oil and gas wells and more particularly, to a rotating blowout preventor mounted on the wellhead or on primary blowout preventors bolted to the wellhead, to pressure-seal the interior of the well casing and permit forced circulation of drilling fluid through the well during drilling operations. The rotating blowout preventor of this invention includes a housing which is designed to receive a blowout preventor bearing assembly and a hydraulic cylinder-operated clamp mechanism for removably securing the bearing assembly in the housing and providing ready access to the components of the bearing assembly and dual stripper rubbers provided in the bearing assembly. A conventional drilling string is inserted or "stabbed" through the blowout preventor bearing assembly, including the two base stripper rubber units rotatably mounted in the blowout preventor bearing assembly, to seal the drilling string. The device is designed such that chilled water and/or antifreeze may be circulated through a top pressure seal packing box in the blowout preventor bearing assembly and lubricant is introduced into the top pressure seal packing box for lubricating top and bottom pressure seals, as well as stacked radial and thrust bearings.
Primary features of the rotating blowout preventor of this invention include the circulation of chilled water and/or antifreeze into the top seal packing box and using a hydraulically-operated clamp to secure the blowout preventor bearing assembly in the stationary housing, to both cool the pressure seals and provide access to the spaced rotating stripper rubbers and internal bearing assembly components, respectively. The clamp can be utilized to facilitate rapid assembly and disassembly of the rotating blowout preventor. Another primary feature is mounting of the dual stripper rubbers in the blowout preventor bearing assembly on the fixed housing to facilitate superior sealing of the stripper rubbers on the kelly or drilling string during drilling or other well operations. Still another important feature is lubrication of the respective seals and bearings and offsetting well pressure on key shaft pressure seals by introducing the lubricant under pressure into the bearing assembly top pressure seal packing box.
Oil, gas, water and geothermal wells are typically drilled with a drill bit connected to a hollow drill string which is inserted into a well casing cemented in the well bore. A drilling head is attached to the well casing, wellhead or to associated blowout preventor equipment, for the purposes of sealing the interior of the well casing from the surface and facilitating forced circulation of drilling fluid through the well while drilling. In the more commonly used forward circulation drilling technique, drilling fluid is pumped downwardly through the bore of the hollow drill string, out the bottom of the bore and then upwardly through the annulus defined by the drill string and the interior of the well casing and subsequently, from the drill string side outlet at the housing. In reverse circulation, the drilling fluid is pumped directly through the side outlet and the annulus between the drill string and the well casing and subsequently upwardly through the drill string bore and from the well.
Prior art drilling heads typically include a stationary body which carries a rotatable spindle operated by a kelly apparatus. One or more seals or packing elements, sometimes referred to as stripper packers or stripper rubbers, is carried by the spindle to seal the periphery of the kelly or the drive tube or sections of the drill pipe, whichever may be passing through the spindle, and thus confine the fluid pressure in the well casing to prevent the drilling fluid from escaping between the rotating spindle and the drilling string. As modern wells are drilled to ever deeper depths, greater temperatures and pressures are encountered, thus sometimes causing steam or hot water vapor at the drilling head. These rigorous drilling conditions pose increased risks to rig personnel from accidental scalding, burns or contamination by steam, hot water and hot, caustic well fluids.
2. Description of the Prior Art
Among the patents which relate to rotating blowout preventors are the following: U.S. Pat. No. 4,783,084, dated Nov. 8, 1988, to Biffle; U.S. Pat. No. 3,965,987, dated Jun. 29, 1976, also to Biffle; U.S. Pat. No. 3,868,832, dated Mar. 4, 1975, also to Biffle; U.S. Pat. No. 4,406,333, dated Sep. 27, 1983 to Adams; U.S. Pat. No. 4,423,776, dated Jan. 3, 1984, to Wagoner, et al; U.S. Pat. No. 4,304,310, dated Dec. 8, 1981, to Garrett; U.S. Pat. No. 4,157,186, dated Jun. 5, 1979, to Murray, et al; U.S. Pat. No. 4,312,404, dated Jan. 26, 1982, to Morrow; U.S. Pat. No. 4,398,599, dated Aug. 16, 1983, to Murray; and U.S. Pat. No. 3,128,614, dated Apr. 14, 1964, to L. S. Auer.
It is an object of this invention to provide a rotating blowout preventor which is characterized by a blowout preventor housing, a clamp mounted on the housing and the housing attached to the well casing, wellhead or other blowout preventor equipment to facilitate removably mounting a blowout preventor bearing assembly in the housing on a housing gasket, while drilling or servicing the well.
Another object of this invention is to provide a dual stripper rubber rotating blowout preventor for containing internal well pressure at the well head, which rotating blowout preventor includes fluid ports communicating with top pressure seals for cooling, lubricating and exerting pressure on the pressure seals and at least partially offsetting well pressure application to the lower pressure seals to minimize deformation and failure of the pressure seals.
A still further object of this invention is to provide a new and improved rotating blowout preventor which is characterized by a blowout preventor bearing assembly fitted with at least two vertically spaced stripper rubber seals, the top stripper rubber seal of which is mounted in a rotating top rubber pot attached to a rotatable inner barrel and the bottom stripper rubber also secured to the rotating inner barrel in the blowout preventor and further including a clamp which is capable of tightening on the blowout preventor housing and bearing assembly to removably secure the bearing assembly inside the housing against a housing gasket.